From 43d18fd59efb58004daa68f0161277efc423deef Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Wed, 22 May 2024 23:29:58 +0200
Subject: [PATCH] Support MarginL and MarginR in SSA subtitles (DoM #2811).

---
 src/ssa_reader.cc               | 50 ++++++++++++++++++++++++++++++++-
 src/ssa_reader.h                |  8 +++++-
 test/data/horizontal_margin.ssa | 23 +++++++++++++++
 test/ssa_reader_test.cc         | 46 ++++++++++++++++++++++++++----
 4 files changed, 119 insertions(+), 8 deletions(-)
 create mode 100644 test/data/horizontal_margin.ssa

diff --git a/src/ssa_reader.cc b/src/ssa_reader.cc
index 262bba7..1302b6b 100644
--- a/src/ssa_reader.cc
+++ b/src/ssa_reader.cc
@@ -149,6 +149,10 @@ public:
 				}
 			} else if (keys[i] == "MarginV") {
 				vertical_margin = raw_convert<int> (style[i]);
+			} else if (keys[i] == "MarginL") {
+				left_margin = raw_convert<int>(style[i]);
+			} else if (keys[i] == "MarginR") {
+				right_margin = raw_convert<int>(style[i]);
 			}
 		}
 	}
@@ -166,6 +170,8 @@ public:
 	HorizontalReference horizontal_reference;
 	VerticalReference vertical_reference;
 	int vertical_margin;
+	int left_margin = 0;
+	int right_margin = 0;
 
 private:
 	Colour colour (string c) const
@@ -185,6 +191,24 @@ private:
 	}
 };
 
+
+void
+SSAReader::Context::update_horizontal_position(RawSubtitle& sub) const
+{
+	switch (sub.horizontal_position.reference) {
+	case LEFT_OF_SCREEN:
+		sub.horizontal_position.proportional = static_cast<float>(left_margin) / play_res_x;
+		break;
+	case HORIZONTAL_CENTRE_OF_SCREEN:
+		sub.horizontal_position.proportional = static_cast<float>(left_margin - right_margin) / (2 * play_res_x);
+		break;
+	case RIGHT_OF_SCREEN:
+		sub.horizontal_position.proportional = static_cast<float>(right_margin) / play_res_x;
+		break;
+	}
+}
+
+
 Time
 SSAReader::parse_time (string t) const
 {
@@ -218,30 +242,39 @@ SSAReader::parse_tag(RawSubtitle& sub, string tag, Context const& context)
 	} else if (tag == "\\an1") {
 		sub.horizontal_position.reference = sub::LEFT_OF_SCREEN;
 		sub.vertical_position.reference = sub::BOTTOM_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an2") {
 		sub.horizontal_position.reference = sub::HORIZONTAL_CENTRE_OF_SCREEN;
 		sub.vertical_position.reference = sub::BOTTOM_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an3") {
 		sub.horizontal_position.reference = sub::RIGHT_OF_SCREEN;
 		sub.vertical_position.reference = sub::BOTTOM_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an4") {
 		sub.horizontal_position.reference = sub::LEFT_OF_SCREEN;
 		sub.vertical_position.reference = sub::VERTICAL_CENTRE_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an5") {
 		sub.horizontal_position.reference = sub::HORIZONTAL_CENTRE_OF_SCREEN;
 		sub.vertical_position.reference = sub::VERTICAL_CENTRE_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an6") {
 		sub.horizontal_position.reference = sub::RIGHT_OF_SCREEN;
 		sub.vertical_position.reference = sub::VERTICAL_CENTRE_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an7") {
 		sub.horizontal_position.reference = sub::LEFT_OF_SCREEN;
 		sub.vertical_position.reference = sub::TOP_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an8") {
 		sub.horizontal_position.reference = sub::HORIZONTAL_CENTRE_OF_SCREEN;
 		sub.vertical_position.reference = sub::TOP_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (tag == "\\an9") {
 		sub.horizontal_position.reference = sub::RIGHT_OF_SCREEN;
 		sub.vertical_position.reference = sub::TOP_OF_SCREEN;
+		context.update_horizontal_position(sub);
 	} else if (boost::starts_with(tag, "\\pos")) {
 		vector<string> bits;
 		boost::algorithm::split (bits, tag, boost::is_any_of("(,"));
@@ -293,6 +326,8 @@ SSAReader::parse_line(RawSubtitle base, string line, Context const& context)
 	 */
 	current.vertical_position.proportional = 0;
 
+	context.update_horizontal_position(current);
+
 	/* We must have a font size, as there could be a margin specified
 	   in pixels and in that case we must know how big the subtitle
 	   lines are to work out the position on screen.
@@ -477,6 +512,8 @@ SSAReader::read (function<optional<string> ()> get_line)
 
 				RawSubtitle sub;
 				optional<Style> style;
+				int left_margin = 0;
+				int right_margin = 0;
 
 				for (size_t i = 0; i < event.size(); ++i) {
 					trim (event[i]);
@@ -512,13 +549,24 @@ SSAReader::read (function<optional<string> ()> get_line)
 						if (sub.vertical_position.reference != sub::VERTICAL_CENTRE_OF_SCREEN) {
 							sub.vertical_position.proportional = float(style->vertical_margin) / play_res_y;
 						}
+						left_margin = style->left_margin;
+						right_margin = style->right_margin;
 					} else if (event_format[i] == "MarginV") {
 						if (event[i] != "0" && sub.vertical_position.reference != sub::VERTICAL_CENTRE_OF_SCREEN) {
 							/* Override the style if its non-zero */
 							sub.vertical_position.proportional = raw_convert<float>(event[i]) / play_res_y;
 						}
+					} else if (event_format[i] == "MarginL") {
+						if (event[i] != "0") {
+							left_margin = raw_convert<int>(event[i]);
+						}
+					} else if (event_format[i] == "MarginR") {
+						if (event[i] != "0") {
+							right_margin = raw_convert<int>(event[i]);
+						}
 					} else if (event_format[i] == "Text") {
-						for (auto j: parse_line(sub, event[i], Context(play_res_x, play_res_y, style ? style->primary_colour : Colour(1, 1, 1)))) {
+						auto context = Context(play_res_x, play_res_y, style ? style->primary_colour : Colour(1, 1, 1), left_margin, right_margin);
+						for (auto j: parse_line(sub, event[i], context)) {
 							_subs.push_back (j);
 						}
 					}
diff --git a/src/ssa_reader.h b/src/ssa_reader.h
index 5de660c..e8c2a52 100644
--- a/src/ssa_reader.h
+++ b/src/ssa_reader.h
@@ -44,15 +44,21 @@ public:
 	class Context
 	{
 	public:
-		Context(int play_res_x_, int play_res_y_, Colour primary_colour_)
+		Context(int play_res_x_, int play_res_y_, Colour primary_colour_, int left_margin_ = 0, int right_margin_ = 0)
 			: play_res_x(play_res_x_)
 			, play_res_y(play_res_y_)
 			, primary_colour(primary_colour_)
+			, left_margin(left_margin_)
+			, right_margin(right_margin_)
 		{}
 
 		int play_res_x;
 		int play_res_y;
 		Colour primary_colour;
+		int left_margin;
+		int right_margin;
+
+		void update_horizontal_position(RawSubtitle& sub) const;
 	};
 
 	static std::vector<RawSubtitle> parse_line(RawSubtitle base, std::string line, Context const& context);
diff --git a/test/data/horizontal_margin.ssa b/test/data/horizontal_margin.ssa
new file mode 100644
index 0000000..c5a9f9e
--- /dev/null
+++ b/test/data/horizontal_margin.ssa
@@ -0,0 +1,23 @@
+[Script Info]
+Title: libsub test
+ScriptType: v4.00
+WrapStyle: 0
+ScaledBorderAndShadow: yes
+PlayResX: 1920
+PlayResY: 1080
+
+[V4 Styles]
+Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, TertiaryColour, BackColour, Bold, Italic, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, AlphaLevel, Encoding
+Style: Default,Arial,20,16777215,255,0,0,0,0,1,2,2,2,200,100,10,0,1
+
+[Fonts]
+
+[Graphics]
+
+[Events]
+Format: Marked, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
+Dialogue: Marked=0,0:00:01.23,0:00:04.55,Default,,100,0,0,,Hello world
+Dialogue: Marked=0,0:01:01.23,0:01:04.55,Default,,10,0,0,,Left of centre
+Dialogue: Marked=0,0:02:01.23,0:02:04.55,Default,,10,0,0,,{\an4}Left
+Dialogue: Marked=0,0:03:01.23,0:03:04.55,Default,,10,0,0,,{\an6}Right
+Dialogue: Marked=0,0:04:01.23,0:04:04.55,Default,,0,100,0,,{\an4}Style left
diff --git a/test/ssa_reader_test.cc b/test/ssa_reader_test.cc
index 89a543c..8820bf4 100644
--- a/test/ssa_reader_test.cc
+++ b/test/ssa_reader_test.cc
@@ -254,7 +254,7 @@ BOOST_AUTO_TEST_CASE (ssa_reader_test3)
 	/* Alignments */
 
 	SUB_START (sub::Time::from_hms (0, 0, 9, 230), sub::Time::from_hms (0, 0, 11, 560));
-	LINE ((10.0 / 1080), sub::BOTTOM_OF_SCREEN, 0, sub::LEFT_OF_SCREEN);
+	LINE ((10.0 / 1080), sub::BOTTOM_OF_SCREEN, (10.0 / 1920), sub::LEFT_OF_SCREEN);
 	BLOCK("bottom left", "Arial", fs(20), false, false, false);
 	SUB_END ();
 
@@ -264,13 +264,13 @@ BOOST_AUTO_TEST_CASE (ssa_reader_test3)
 	SUB_END ();
 
 	SUB_START (sub::Time::from_hms (0, 0, 9, 250), sub::Time::from_hms (0, 0, 11, 560));
-	LINE ((10.0 / 1080), sub::BOTTOM_OF_SCREEN, 0, sub::RIGHT_OF_SCREEN);
+	LINE ((10.0 / 1080), sub::BOTTOM_OF_SCREEN, (10.0 / 1920), sub::RIGHT_OF_SCREEN);
 	BLOCK("bottom right", "Arial", fs(20), false, false, false);
 	SUB_END ();
 
 	SUB_START (sub::Time::from_hms (0, 0, 9, 260), sub::Time::from_hms (0, 0, 11, 560));
 	/* Position is half of a 20pt line (with line spacing) above vertical centre */
-	LINE (-vp(10), sub::VERTICAL_CENTRE_OF_SCREEN, 0, sub::LEFT_OF_SCREEN);
+	LINE (-vp(10), sub::VERTICAL_CENTRE_OF_SCREEN, (10.0 / 1920), sub::LEFT_OF_SCREEN);
 	BLOCK("middle left", "Arial", fs(20), false, false, false);
 	SUB_END ();
 
@@ -280,12 +280,12 @@ BOOST_AUTO_TEST_CASE (ssa_reader_test3)
 	SUB_END ();
 
 	SUB_START (sub::Time::from_hms (0, 0, 9, 280), sub::Time::from_hms (0, 0, 11, 560));
-	LINE (-vp(10), sub::VERTICAL_CENTRE_OF_SCREEN, 0, sub::RIGHT_OF_SCREEN);
+	LINE (-vp(10), sub::VERTICAL_CENTRE_OF_SCREEN, (10.0 / 1920), sub::RIGHT_OF_SCREEN);
 	BLOCK("middle right", "Arial", fs(20), false, false, false);
 	SUB_END ();
 
 	SUB_START (sub::Time::from_hms (0, 0, 9, 290), sub::Time::from_hms (0, 0, 11, 560));
-	LINE ((10.0 / 1080), sub::TOP_OF_SCREEN, 0, sub::LEFT_OF_SCREEN);
+	LINE ((10.0 / 1080), sub::TOP_OF_SCREEN, (10.0 / 1920), sub::LEFT_OF_SCREEN);
 	BLOCK("top left", "Arial", fs(20), false, false, false);
 	SUB_END ();
 
@@ -295,7 +295,7 @@ BOOST_AUTO_TEST_CASE (ssa_reader_test3)
 	SUB_END ();
 
 	SUB_START (sub::Time::from_hms (0, 0, 9, 310), sub::Time::from_hms (0, 0, 11, 560));
-	LINE ((10.0 / 1080), sub::TOP_OF_SCREEN, 0, sub::RIGHT_OF_SCREEN);
+	LINE ((10.0 / 1080), sub::TOP_OF_SCREEN, (10.0 / 1920), sub::RIGHT_OF_SCREEN);
 	BLOCK("top right", "Arial", fs(20), false, false, false);
 	SUB_END ();
 
@@ -637,3 +637,37 @@ BOOST_AUTO_TEST_CASE (ssa_reader_c)
 	test_c("", "ff00ff");
 }
 
+
+BOOST_AUTO_TEST_CASE(ssa_reader_horizontal_margin)
+{
+	auto subs = read_file("test/data/horizontal_margin.ssa");
+	BOOST_REQUIRE_EQUAL(subs.size(), 5U);
+
+	int n = 0;
+
+	BOOST_REQUIRE_EQUAL(subs[n].lines.size(), 1U);
+	BOOST_CHECK(subs[n].lines[0].horizontal_position.reference == sub::HORIZONTAL_CENTRE_OF_SCREEN);
+	BOOST_CHECK_CLOSE(subs[n].lines[0].horizontal_position.proportional, 0, 1);
+	++n;
+
+	BOOST_REQUIRE_EQUAL(subs[n].lines.size(), 1U);
+	BOOST_CHECK(subs[n].lines[0].horizontal_position.reference == sub::HORIZONTAL_CENTRE_OF_SCREEN);
+	BOOST_CHECK_CLOSE(subs[n].lines[0].horizontal_position.proportional, -90.0f / (2 * 1920.0f), 1);
+	++n;
+
+	BOOST_REQUIRE_EQUAL(subs[n].lines.size(), 1U);
+	BOOST_CHECK(subs[n].lines[0].horizontal_position.reference == sub::LEFT_OF_SCREEN);
+	BOOST_CHECK_CLOSE(subs[n].lines[0].horizontal_position.proportional, 10.0f / 1920.f, 1);
+	++n;
+
+	BOOST_REQUIRE_EQUAL(subs[n].lines.size(), 1U);
+	BOOST_CHECK(subs[n].lines[0].horizontal_position.reference == sub::RIGHT_OF_SCREEN);
+	BOOST_CHECK_CLOSE(subs[n].lines[0].horizontal_position.proportional, 100.0f / 1920.f, 1);
+	++n;
+
+	BOOST_REQUIRE_EQUAL(subs[n].lines.size(), 1U);
+	BOOST_CHECK(subs[n].lines[0].horizontal_position.reference == sub::LEFT_OF_SCREEN);
+	BOOST_CHECK_CLOSE(subs[n].lines[0].horizontal_position.proportional, 200.0f / 1920.f, 1);
+	++n;
+}
+
-- 
2.30.2